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1 Q2C6 Nice, October 17th 2013
Universität Bremen
Sasha Buchman for the mSTAR team
October 17th , 2013
mSTAR: Space-Time Asymmetry Research
Testing Lorentz Invariance in Low-Earth Orbit
2 Q2C6 Nice, October 17th 2013
Universität Bremen
Kinematic Approach to LIV
Is the CMB a preferred frame?
22
2sinc
vvC
c
vvC
c
c CMBINSTRKT
CMBINSTRINSTRMM
Michelson
Morley
Coefficient
Kennedy
Thorndike
Coefficient
vINSTR, vCMB = velocities of instrument, preferred frame (PF)
INSTR = angle of light beam (instrument) to the PF
in Special Relativity CMM = CKT = 0
RMS approach:
-Robertson (1949)
-Mansouri &
-Sexl (1977)
3 Q2C6 Nice, October 17th 2013
Universität Bremen
Upper: the derived quadrupole (temperature range ±35 micro-K). Lower: the derived octopole (temperature range ±35 micro-K). Cross and star signs indicate axes of the quadrupole and octopole, respectively, around which the angular momentum dispersion is maximized. -Planck collaboration, arXiv, 1303.5083v1
Planck CMB data analysis (2013)
4 Q2C6 Nice, October 17th 2013
Universität Bremen Why Measure c Invariance?
Colladay and Kostelecky (1997)
“The natural scale for a fundamental theory including gravity is
governed by the Planck mass MP, which is about 17 orders of
magnitude greater than the electroweak scale mW associated
with the standard model. This suggests that observable
experimental signals from a fundamental theory might be
expected to be suppressed by some power of the ratio:
The mSTAR sensitivity could close that gap
1710~P
W
M
mr
5 Q2C6 Nice, October 17th 2013
Universität Bremen
Why KT in Space?
Kennedy-Thorndike signal enhancement
Signal modulated at satellite orbital variation ~1.5 hr
Signal modulated at orbital velocity differences 7 km/s
Diurnal Earth rotation signal <0.30 km/s @ 24 hr
Yearly Earth orbital motion signal at 30 km/s @ 8766 hr
Disturbance reduction Microgravity
Seismic quietness
Relaxed stress due to self weight
Far away from time dependent gravity gradient noises
KT Improvement in Space:
Faster signal modulation 4 ( 16)
Higher velocity modulation 20 to 30
Other considerations ~ 1 to 3
Net Overall Advantage 100
6 Q2C6 Nice, October 17th 2013
Universität Bremen
A velocity-dependent LIV would cause a c/c variation at the orbital rate
Measuring KT
= 90º
= 270º
= 180º
= 0º
vCMB, velocity of
preferred frame
vINSTR, velocity of
orbiting instrument
17
210
2KT
CMBINSTR Cc
vv
KT Coefficient
0º 90º 180º 360º 270º
c/c
8 Q2C6 Nice, October 17th 2013
Universität Bremen
miniSTAR conceptual diagram
CUT
9 Q2C6 Nice, October 17th 2013
Universität Bremen
mSTAR Concept
Science
1) Lorentz Invariance Violations
2) Velocity boost c dependence
“Kennedy-Thorndike Experiment”
3) >100x state of the art
Technology
1) “Capable” small satellite bus
100 kg, 120 W, secondary payload
2) Advanced frequency standards
3) Precision thermal control
Education
1) Graduate & Undergraduate
2) 3-5 year projects
3) Student led tasks
Science & Technology
on Small Satellites
Education driven
International collaborations
Lipa, et. al. “Prospects for an advanced Kennedy-Thorndike
experiment in low Earth orbit” arXiv:1203.3914v1[gr-qc]
10 Q2C6 Nice, October 17th 2013
Universität Bremen mSTAR Collaboration
Collaborating Institutions
Main Contributions
ALL Science and EP&O
KACST Spacecraft, Launch,
Mission Operations
DLR & Bremen Iodine Clock,
Instrument Integration
Mission Operations
JCOE Optical cavity to TRL 4
Ames Research Center Optical cavity to TRL 6
Mission Operations
Kingdom of Saudi Arabia
King Abdulaziz City for Science
and Technology (KACST)
KACST – Stanford JCOE
Germany
German Aerospace Center (DLR)
Bremen University
ZARM
Humboldt University, Berlin
United States
NASA Ames Research Center (ARC)
KACST – Stanford JCOE
Stanford University
11 Q2C6 Nice, October 17th 2013
Universität Bremen
mSTAR Technology Challenges
Optical cavities
Molecular clocks
Hz10 15ff
Advanced frequency standards
Thermal shields
Control algorithms
Optical thermometry
12
9
10
10
shieldOutershieldInner
shieldOutershieldInner
FF
TT
nano Kelvin thermal control
12 Q2C6 Nice, October 17th 2013
Universität Bremen
History of KT measurements
KT Coefficient
KT
co
effic
ien
t
10-1
10-9
10-7
10-5
10-3
10-11
mSTAR
1920 1940 1960 1980 2000 2020
Year
R.J. Kennedy E.M. Thorndike
13 Q2C6 Nice, October 17th 2013
Universität Bremen
clock based on atomic transition
clock based on length standard
beat measurement
with
varying laboratory velocity
Modern Kennedy-Thorndike Tests
Universität Bremen
14 Q2C6 Nice, October 17th 2013
Universität Bremen
RF modulation obtained by frequency generation board
RF demodulation executed digitally by FPGA board (with RF ADC channels)
Digital VCO by onboard FPGA
Laser PZT and Temp controlled by FPGA
Science signal contained in the digital VCO error signal
miniSTAR optical diagram
15 Q2C6 Nice, October 17th 2013
Universität Bremen
Vortrag > Autor > Dokumentname > Datum
Thermal noise floor of cavities
State of the art: Iodine vs. cavity
Orbital period
mSTAR
Universität Bremen
16 Q2C6 Nice, October 17th 2013
Universität Bremen Iodine Frequency Reference EBB Level
55cm
25
cm
Spectroscopy Unit,
Braxmaier et al, 2013
Universität Bremen
17 Q2C6 Nice, October 17th 2013
Universität Bremen Iodine Frequency Reference EM Level
Spectroscopy Unit,
Braxmaier et al, 2013
Universität Bremen
Next steps:
EBB to EM level
Space qualification
18 Q2C6 Nice, October 17th 2013
Universität Bremen Optical cavity
Key optical cavity parameters:
L/L < 10-17 at orbit and harmonics
with 2 years of data
L/L < 10-17 at twice spin period
with 2 years of data
Derived requirements:
Expansion coefficient: < 10-9 per K
Operating temperature: within 1 mK
of expansion null (~ 15°C nom)
External strain attenuation: > 1012
Stiffness: L/L < 10-9 per g, 3-axis
Implied material: ULE glass
19 Q2C6 Nice, October 17th 2013
Universität Bremen Optical cavity work at Stanford
1064nm
1550nm
300 mm Iodine cell
20 Q2C6 Nice, October 17th 2013
Universität Bremen Thermal enclosure
Main Requirements:
Thermal stability
Stress attenuation
Launch and space compatible
Thermal performance:
Cavity L/L < 10-17 (2 yr data) at:
- orbital period and harmonics
- twice spin period
Derived requirements <2 yr>:
Stability of 10-8 K at orbit
Gradient ~ 10-9 K/cm at orbit
Maintain temperature to 1 mK
21 Q2C6 Nice, October 17th 2013
Universität Bremen Thermal enclosure & cavity
(GRACE-FO)
22 Q2C6 Nice, October 17th 2013
Universität Bremen
mSTAR mission characteristics
Secondary payload: Saudi Sat 4 (UV-LED Sat - April 2014)
Circular sun-synchronous ~ 650 km orbit
Launch 2017
2-year mission lifetime
23 Q2C6 Nice, October 17th 2013
Universität Bremen
STAR Geometry and Frequencies:
• Spacecraft spin rate (nominal): spin = 1/(100 sec) = 10 mHz
• Orbit: 600 km Sun-sync (nominal): orbit = 1/(98 min) = 0.17 mHz
• Earth’s orbital rate: Earth = 1/(1 yr) = 32 nHz
spin
orbi
t
Earth
Sun
Earth
STAR
1 Au
650
km
24 Q2C6 Nice, October 17th 2013
Universität Bremen
mSTAR Status
2008 Concept proposed as a NASA MOO SMEX
2011 Second proposal submitted as NASA MOO
Reviews pointed out some weaknesses
TRL levels, Complexity, Cost
Current efforts:
Bring instrument to TRL 5
Using internal resources
Contributions from partners
Reduce instrument complexity
25 Q2C6 Nice, October 17th 2013
Universität Bremen
mSTAR Schedule
mSTAR Milestone Draft
Phase Name Activity Completion Months
1 Nice Workshop Draft Proposal Oct-2013 1
2 Requirements Review Design study Apr-2014 6
3 PDR HW & SW development Jan-2015 9
4 CDR HW & SW to TRL 4 Jan-2016 12
5 Integration Review HW & SW to TRL 6 Jan-2017 12
6 Launch Review Integrated System Jul-2017 6
7 Launch Launch activities Dec-2017 6
8 Science Mission Mission Operations Dec-2019 24
9 Science Results Data Analysis Dec-2020 12
26 Q2C6 Nice, October 17th 2013
Universität Bremen Questions?
Thank You
Kostelecky, Scientific American, 2002